Rebecca ReichRebecca ReichMay 24 2011
h Who am I?
d d h l k Audio / Acoustics around the clock
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
B. Eng, electrical, Minor Arts
NRC Women in Engineering and Science scholarshipg g p• classroom and concert hall acoustics
S.M., Media Arts and Scienceshl l Cochlear implants
how do they sound when music plays through them?
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Programming 1’s and 0’s Programming user software
Customer technical supportsupport
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
One year in Copenhagen, DK Customer technical support
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
C h i l (fi h ) Customer technical support (five months) Manager, customer technical support team China, Japan, Canada
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
• Flexible• People job• Learn new stuff!www.mitacs.ca
•$7 500 industry7 5 y•$7 500 Mitacs/FQRNT$15 000
$10 000 min for student
$5000flexible
•$36 000 industry•$44 000 Mitacs/FQRNT$80 000
$20 000$10 000 $10 000 $10 000
$10 000 $10 000 $10 000 flexible$10 000 $10 000 $10 000 internships
Let’s get startedLet’s get started…
f f Sound is a form of energy (like electricity or light)
d d h l l b Sound is made when air molecules vibrate and move in a pattern waves
Animation courtesy of Dr. Dan Russell, Kettering University
Particle motion is a function of spaceParticle motion is a function of space(displacement, amplitude)
and time
Longitudinalwave: particle motion is parallel to motion of disturbance
created by moving object
Wave causes areas of compression (high ) d f i (l ) W
created by moving object
pressure) and rarefaction (low pressure). We call this PRESSURE waves
c = 343m/s (air, 20oC)
we INTERPRET sound waves
F Frequency: how often the particles are moving back and forth:
# of complete back‐and‐forth vibrationsof a particle of the medium Hertz:p
per unit of time # cycles per second
H H20Hz – 20 000HzSensation of frequency = pitch
G li d f di b Greater amplitude of disturbance causes greater displacement (amplitude) of particles
More amplitude more energy More amplitude more energy Intensity = power/area (Watts/m2) Move away from sound ,intensity decreases Move away from sound ,intensity decreases (inverse square)
Humans can detect as low as 1*10‐12W/m2, ,and as high as 1 billion times this!
Due to large range: dB d 1*10‐12W/m2 = 0 dB
sleep
workwork
wake
play
f f Your alarm‐clock radio: fast facts Why does Boston Acoustics sound better 06:00than Accurian?
Looking at an average over a window of time…
Wh d d d i i i th Why does everyone sound good singing in the shower?
06:15
ACOUSTICS: study of waves in a medium
5
fl d f d b b d Direct, Reflected, Refracted, Absorbed
f Hard surfaces little sound absorbed (ceramic tile) many reflections reverberation
i th h ld f ~50ms is threshold for hearing echo
Small space accumulation of reflections increases volume you sound more powerful!
Resonant cavity Shower stall dimensions
dcause standing waves at low frequencies; vocals in this range will be boostedthis range will be boosted
Car stereo acoustics “dead” sound environment, depends on materials 08:00(leather vs. upholstry) transitory (windows open vs. closed) loud: riding the volume knob
l b d l d b f Single‐band compressor, loud bass information modulates gain of the entire audio signal suboptimal maximum perceived loudness & gain suboptimal maximum perceived loudness & gain pumping
Listening to iPod [Portnuff] listening to earbuds for 90 minutes/day at 80% volume is probably safe for long‐term hearing (softer is better: you can safely tune in at 70% volume for about 4½ hours a day )volume for about 4½ hours a day.)
~ one in five teenagers had some kind of hearing loss in 2005‐2006, up from 15% of teenagers in the late 1980s and 2005 2006, up from 15% of teenagers in the late 1980s and early 90s, according to a study of nearly 5,000 people age 12 to 19 published in the Journal of the American Medical Association.
Th i ti f t t d The maximum exposure time for unprotected ears per day at 90 dB is 8 hours.
For every 5 dB increase in volume the maximum For every 5 dB increase in volume, the maximum exposure time is cut in half. 95 dB = 4 hours95 4 100 dB = 2 hours 110 dB = 30 minutes 120 dB = 7.5 minutes
Apple set 100dB limit in Europe, still 115dB in USAUSA
f Dynamic compression a reality of modern music recordings (louder is better)
l f Causes listener fatigue
08:45
I l i l l b dB(A) d b
45
In general, noise levels above 45‐50 dB(A) tend to be disturbing
Speech Intelligibility Index (SII): how well speech can be understood in the presence of noise.p
range: 0 (perfect privacy) to (perfect intelligibility) Theatres and auditoriums need high SII values, but offices
and other private locations need low SII SII <= 0 2 gives employees speech privacy and blocks most SII <= 0.2 gives employees speech privacy and blocks most
acoustical distractions
C ili d fl Ceiling and floor Partitions (partial‐height screens) Workstation and Occupant Orientation Workstation and Occupant Orientation Lighting fixtures (flat vs grill) Noise Masking SystemNoise Masking System
N i ll ti h d h Noise‐cancellation headphones Active vs. Passive Active: 09:00
▪ produce “anti‐noise”▪ require battery▪ cancel low‐frequency continuous
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cancel low frequency, continuous sound actively, high‐frequency through design
Passive▪ physical block; works over wide range▪ no battery▪ weaker bass response (due to speaker weaker bass response (due to speaker size)
Your hearing… getting old…”eh?”
18:00
• outer/middle ear• often reversible
conductive
• inner ear• not reversible
b l t dsensorineural
• can be age‐related
Symptoms Symptoms Certain sounds seem overly loud Difficulty hearing things in noisy areas High‐pitched sounds such as "s" or "th" are hard to distinguish from one another
Men's voices are easier to hear than womens.
Other people's voices sound mumbled 20% over 65p por slurred
Ringing in the ears “I hear but I can’t understand”
40% over 75
80% nursing home residents
f Not just amplifiers ex. frequency translation
Adapt to environment cocktail party effect
Connected bluetooth bilateral communication
36 000 people world 36,000 people world‐wide received cochlear implants over the last t d dtwo decades.
FDA‐approved 1985 (adults), 1990 (children)Ad lt b Adults can now be considered candidates if they have severe‐to‐
f d h i l profound hearing loss and understand less than 50% of sentences
k t thspoken to themviolin, processedviolin
ffnoises off!
22:00